Tiny Green Bug May Be First Photosynthetic Animal

Pea aphids may have an unprecedented ability to harvest sunlight, and use the energy for metabolic purposes. It would make it the only species of animal known to have photosynthesis-like powers.

[partner id=”wireduk”]It comes down to carotenoids, which are a type of pigment used in animals for crucial functions like vision, bone growth and vitamin production. All known animals obtain these by eating the plants, algae and fungi that naturally synthesize the orange-red compounds.

Back in 2010, University of Arizona biologists researcher Nancy Moran and Tyler Jarvik discovered that pea aphids can make their own carotenoids, like a plant. “What happened is a fungal gene got into an aphid and was copied,”said Moran in a press release.

Entomologist Alain Robichon, of the Sophia Agrobiotech Institute in France, wanted to find out why the insects make such metabolically expensive chemicals.

Carotenoids are responsible for aphid body color, and the researchers found that insects changed color depending on environmental conditions. In optimal environments, aphids make a medium amount of carotenoids and come out orange. In the cold, the insects have a high level of carotenoids and are green. In areas with limited resources, aphids are almost devoid of the pigment and are born white.

The team then measured the aphids’ levels of adenosine triphosphate (ATP) — a way to measure energy transfer in living organisms — and received striking results. Green aphids make significantly more ATP than white ones, and orange aphids made more ATP while exposed to sunlight than when kept in the dark.

The researchers also crushed the orange aphids and purified their carotenoids, to demonstrate that it was these extracts that could absorb light and pass this energy on. This all suggests that the synthesized pigments may contribute to a system of photo-induced electron transfer, where the aphids can harness energy from the sunlight.

The team warns that more research will be needed before we can be sure that aphids truly have photosynthesis-like abilities. The researchers also speculate that the ability might be used as a back-up, during times of environmental stress.